Electromagnetic relay



July 1; 1941.

w. H. D. YULE BLECTROIAGHBTIC RELAY l Filed Nov. 6, 1943 Patented July l, 1947 ELECTROMAGNETIC RELAY William Henry Drury Yule, London. England, as-

signor, by mesne assignments, to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application November 6, 1943, Serial No. 509,214 In Great Britain December 31, 1942 12 claims. 1

'I'his invention relates to electromagnetic relays, and more particularly to relays used in radio-frequency circuits especially at higher frequencies (above 100 mc.). For example, in certain radio-signalling systems, two relays are used on each installation, one having a make contact, and the other a break contact, adjusted so as to give a closely controlled interval (e. g. 2 to 6 milliseconds)` between the functioning of their contacts on both operation and release. Such relays are provided to make or break connection between the dipoles of reflector antennae used in radio-navigation systems. The requirements are 'that they should have low capacitance' vention will 'more lclearly appear from the following description and the appended claims.

The invention will -be described 'with reference to the accompanying drawing in which:

Fig. v1 lis a plan view of a relay in accordance with the invention;

f Fig. 2 is a view of that end of the relay which appears on the right of Fig. 1;

Fig. 3 is a view of that side of the relay-which appearsat the bottom'of Fig. l; and

Fig. 4 is a view of a detail.

The main supporting structure of the relay is in the form of a hollow or ring-like rectangular base-frame II which is of insulating material such Ias ebonite, but preferably of ceramic or moulded material. This frame II is itself mounted upon a panel or other member I 2 by means of two bolts I3 and spacers I4. The operating magnet I5 includes a core I6 which has an enlargement or cross-piece formed at its right-hand or rear end for attachment by means of screws I1 and spacer I8 to the overlying portion of the frame I I. At the left-hand or front end the core is supported for additional rigidity on the frame I I through the intermediary oi a bracket I9. The armature 20 is U-shaped, with its legs straddling the magnet and hinged to the core Vat the'rear 2 end by iiat springs 2i. Flat springs 22 are engaged by studs 23 depending from the underside of the armature. and serve to hold the amature in its unoperated or released position lwhen the magnet is not energised.

The relay contacts which are to fopen or close the circuit under control consist of 'two ilxed contacts spaced apart and a bridge 'between them which is displaceable by the armature. In the embodiment now being described, the contacts are normally closed, i. e. the circuit is broken when the magnet is energised. As shown the iixed contacts :are mounted upon the inner extremities of spring strips '24 and 25 which are ixed in line with fone another on opposite sides of the frame II. Cooperating with these ilxed contacts are moving contacts which are mounted lupon a spring strip 25 which bridges the gap between .the two ilxed strips and is mounted on the top of an insulatingl bracket 21 itself ilxed upon the armature. f

'I'he` features and advantages of this arrangement will now be described.

The use of an open or ring-shaped frame II of considerable thickness, which may be made either of ceramic or synthetic moulded material, ensures a high degree of mechanical rigidity and stability, while allowing the amount of dielectric material between springs to be reduced to a minimum. If the frame is suillciently thick. and the core is rigid in itself, the frame may be of a U- shape instead of being ring-shaped. Paths for possible stray capacities, which normally contribute an appreciable proportion of the interelectrode capacitance, are also considerably lengthened.

The'wide spacing (about of the contact members 2l, 25 and 26 from the main relay frame (coil I5 and armature 20), their disposition at right angles to the main axis, and the design of the bracket 2l supporting the centre spring (see Fig. 4), reduce the capacitance between contacts and the relay frame.

The end-to-end arrangement of contact springs 24, 26, 25 greatly reduces the capacitance between them, and places it at the centre-point of the reector, which greatly facilitates the accurate lining-up of the antenna, array.

The feature of using two contact openings in series is specially important as giving very low lever spring on relays of normal construction,

and which is a common source of instability and early failure.

There is a sharper change in capacitance when the contacts open as compared with a single opening. This is important with very high frequencies in ensuring clean keying.

Another feature of interest concerns the attachment of the contact springs without the use of screws or rivets. One of the commonest causes of instability under conditions of vibration or wide variations of temperature and humidity is the loosening of screws, nuts and rivets. Two methods of overcoming this have been tried, and found satisfactory. The spring support may be made from ceramic material, and a. film of metal (such as silver or platinum) deposited on it at the point of attachment, either with or without local glazing of the ceramic. The contact springs can then be soldered to the metallic deposit, using a non-corrosive ilux. It has been found beneiicial to provide a thin metal cap tting over the contact springs and formed over the support, and soldered to them, thus providing soldered surfaces in which the strain on the metal iihn is perpendicular to that imposed by the ilexing of the contact spring itself when the relay operates. A similar technique has been applied for attaching the support of the centre spring to the armature.

Alternatively the spring support may be in the form of a high grade synthetic moulding, the springs being attached by tting over them a suitably shaped cap of similar material secured to the support and keyed to the spring itself by a suitable cement. Such caps are shown at 2l, 29 and 30 in the drawing. Although ceramic is believed vto be more stable than synthetic moulding, assembly may be easier using cemented mouldings: in either case a reduction in the amount of metal associated with the contact springs assists in reducing stray capacitance.

It has been found that timing requirements can be met without dimculty, and are maintained within permissible limits over a relatively wide range of keying current and applied voltage. Operating time can be controlled by variation of the pressure of the restoring springs 22 and such adjustment does not appreciably affect the re.. lease time. The latter has been found substantially independent of adjustment variations, and the required timing difference on release has been obtained by applying a non-inductive shunt to one of the relays (the break), which may be of sufficiently high resistance not to affect the operating timing. It is therefore possible to adjust operate and release timing independently of each other which facilitates maintenance.

What is claimed is:

1. An electromagnetic relay comprising a frame of insulating material defining a hollow space, an electromagnetic coil supported in spaced relation to said frame with its axis extending across said hollow space defined by said frame, an armature supported in operative relation to said electromagnetic coil and in spaced relation to said frame, a pair of contact members supported on opposite sides of said frame across said hollow space with their contact surfaces positioned inwardly of said hollow space in spaced relation to said trame and in spaced relation to each other, said contact members also being supported in spaced relation to said coil and its armature, whereby a low capacitance is maintained between said contact members themselves and between said contact members on the one hand and said coil and its armature on the other hand, and a bridging contact member carried by said armature in spaced relation thereto and positioned so as to bridge thegap between said spaced contact surfaces oi' said pair of contact members and to make and break contact therewith upon repeated operation of said armature by said electromagnetic coil.

2. An electromagnetic relay comprising a frame of insulating material defining a hollow space open at opposite ends thereof, an electromagnetic coil supported with its axis extending centrally across said hollow space transversely of the direction from one open end oi' said space toward the other, an armature supported so as to be positioned adjacent said coil axis and in operative relation to said coil, a pair of contact members supported on opposite sides of said frame across said hollow space in spaced relation to each other and in spaced relation to said coil and its armature so as to maintain a low capacitance between said pair of contact members themselves and between said contact members on the one hand and said coil and its armature on the other hand, and a bridging contact member carried -by said armature in spaced relation Vthereto and positioned so as to bridge the gap between said pair of contact members and to make and break contact therewith upon repeated operation of said armature by said electromagnetic coil.

3. An electromagnetic relay comprising a frame of insulating material extending about a hollow space open at opposite ends thereof, an electromagnet having a core and a coil wound about said core, said magnet being supported at an end thereof upon one side of said frame with the axis of said core extending from said side o! the frame centrally across said hollow space in a plane which is transverse to the direction from one of said opposite open ends of said hollow space toward the other, an armature supported upon said frame adjacent said magnet core in operative relation thereto so as to move transversely of said plane, a pair of elongated contact members mounted on opposite sides of said frame across said hollow space in spaced relation to each other and extending toward each other transversely of the axis of said core to provide a low capacitance therebetween, said contacts being supported in spaced relation to said electromagnet and its armature to maintain a low capacitance between said contact members on the one hand and said electromagnet and its armature on the other hand, and a bridging contact member carried by said armature in spaced relation thereto and positioned so as to bridge the gap between said pair of elongated contact members and to make and break contact therewith upon repeated operation of said armature concomitantly with energization and de-energization of said electromagnet.

4. An electromagnetic relay as dened in claim 3 which comprises means to bias said bridging contact to bridging position with respect to said pair of contact members, said electromagnet and its armature being constructed to open said con tacts against said bias means upon energization of said electromagnet.

5. An electromagnetic relay comprising a frame of insulating material extending about a rectanguiar hollow space open at opposite faces of said frame, an electromagnet having a core supported at its ends upon opposite sides of the rectangle of said frame so as to extend centrally across said rectangular space generally parallel to the faces of said frame, a magnetizing coilwound about said core, a' U shaped member carrying an armature for cooperation with said core and hlngedly supported on one of said opposite sides of said frame so as to straddle said coil substantially in the plane of the axis thereof to provide movement of said' armature in the direction trans- 6 toward the other. an armature pivotally supported on said frame adjacent said supported end of said magnet for movement to and fro relative to the other end of said magnet in said direction hlaterally with respect to said frame, a pair of spaced relation to said frame and on a line exversely of said faces of said frame, two contact l strips respectively attached to the other opposite sides of said lrectangular frame and extending inwardly across said hollow space with their contact surfaces positioned in spaced relation to said frame, said strips being positionedin line with each other on a line extending transversely of the axis of said coil with their contact surfaces in-` spaced relation to one another to provide a low capacitance between said strips, said contact strips also being spaced from said electromagnet and said armature to provide alow capacitance between said strips on the one hand and said coil and said armature on the other hand, and a bridging contact strip carried by said armature in spaced relation thereto and positioned so as to bridge the gap between said two contact strips and to make and break contact therewith upon hinging movement of said U shaped member effected by said electromagnet.

6. An electromagnetic relay comprising aframe ,y transversely of the direction from one open end of said space toward the other, a magnetizing coil wound about said core, a pair of contact strips mounted at points on said frame oppositely positioned across said hollow space and with their ends spaced from each other and extending toward each other in a line transverse to the axis of said core, an armature associated with said electromagnet, a hinging flat spring rigidly connected adjacent its ends respectively to said armature and to said frame to provide hinging movement of said armature about an axis parallel to said line of said pair of contact strips upon energization and de-energization of said electromagnet, and a bridging contact strip carried by said hinging fiat spring in position to bridge the gap between the ends of said spaced contact strips to make and break contact therewith upon 'hinging movement of said armature upon said flat spring, said bridging contact being mounted on said armature in spaced relation thereto so asto provide a low capacitance between said two contact strips and said bridging contact strip on the one hand and said electromagnet and said armature and its support on the other hand.

7. An electromagnetic relay comprising a frame of insulating material defining an open-ended hollow space, a magnet supported at an end thereof upon one side of said frame with the axis of the magnet extending toward the opposite side of the hollow space defined by said frame and oset laterally with respect to said frame in the direction from one open end of said hollow space tending across the hollow space defined by said frame transversely to the axis of said magnet, said contacts being spaced from said magnet and its armature to maintain a Ilow capacitance between said contacts on the one hand and said magnet and its armature on the other hand, said contact members forming a gap therebetween, and a bridging contact member carried by said armature so as to make contact with the contact surfaces of said pair of contact members upon operation of said armature vand to bridge the gap therebetween, said bridging contact member being carried by said armature in spaced relation thereto so as to maintain a low capacitance between said bridging contact member and said armature.'

8. In an electrical relay, in combination, a frame of insulating material defining a hollow space open at opposite ends thereof, a pair of elongated contact members supported with their lengths in alignment with each other on opposite sides of said frame across said hollow space with the contact surfaces thereof positioned inwardly of said hollow space in spaced relation to said frame and in spaced relation to each other to provide a low capacitance therebetween, a bridging contact supported in spaced relation to said frame and for movement into and out of bridging contact with said spaced contact surfaces of said pair of contact members in the direction from one of said opposite open endsof said hollow space toward the other, and electrically energized means for effecting said movement of said bridging contact, said means being positioned in spaced relation to said bridging contact and to said pair of contact members in said direction from one of said open ends of said hollow space toward the other so as to maintain a low capacitance between said bridging contact and said contact members on the one hand and said means for eifecting movement of said bridging contact on the other hand.

9. An electromagnetic relay for controlling currents of radio frequency comprising a frame of insulating material defining an open-ended hollow space," mounting means for supporting said frame in spaced relation to a supporting surface, an electromagnet supported with the axis of said magnet extending centrally across said hollow space and in spaced relation to said frame* between said frame and said supporting surface, an armature mounted in operative relation to said magnet in spaced relation to said frame, a pair of contact members supportedk on said frame in spaced relation to each other with their contact ends extending toward one another across the hollow space defined by said frame transversely of the axis of said magnet, and a bridging contact member supported in spaced relation to said armature and said magnet for movement into and out of engagement with said spaced contact members upon energization and de-energization of said magnet.

10. kThe relay as set forth in claim 1, in which said frame is of ceramic material, and the relay 7 s includes metallic deposits on the frame to which said contacts are soldered. REFERENCES CITED 11. The relay as set forth in claim 1. in which The following references are of record in the said i'rame is of ceramic material having metallic ille of this patent: deposits adjacent the contacts, and the relay in- 8 cludes a metal cap ntted over and soldered to each UNITED STATES PATENTS contact and to the adjacent metallic deposit. Number Name Date 12. The relay as set forth in claim 1, in which 850,205 Bergman Apr. 18, 1907 said trame is of synthetic moulded material, and 1,897,872 Johnson Jan. 8. 1929 the relay includes a can oi.' said material iitted 10 1,717,057 Meuer June 11, 1929 over and cemented to each contact and the frame. 2,120,421 Wager June 14, 1938 2,304,972 Van Vlkenbllrl et ll. Dec. 15, 1942 WILLIAM HENRY DRURY YULE. 2,319,906 Rowe May 25, 1943 

